We came across an interesting article in the engineer regarding how the use of carbon fibre as part of a composite material and electrode in lithium-ion structural batteries could see vast improvements in aircrafts as well as electric vehicles (EVs).
The article points out that structural batteries have been under consideration for electric vehicles for some years. They are energy storage devices which form part of the overall structure of the vehicle: in the bodywork or chassis. In theory, performing “double duty” as part of the structure and the energy storage capability of the vehicle is a method of reducing weight. However, previous prototypes of structural battery systems have been found wanting.
Researchers from Chalmers University of Technology in Sweden have now found a new way of transforming composite panels into batteries. Led by Leif Asp, a professor of material and computational mechanics, the team has been researching how carbon fibres in composites could be used as components of lithium ion batteries formed out of the panelwork itself. “It will also be possible to use the carbon fibre for other purposes such as harvesting kinetic energy, for sensors or for conductors of both energy and data. If all these functions were part of a car or aircraft body, this could reduce the weight by up to 50 per cent,” Asp claimed.
Using carbon as a component in lithium ion batteries is not in itself new; it is an established practice to use carbon – generally in its graphite form or a variant of it – as the positive electrode while lithium metal is the negative. Lithium ions migrate across the battery electrolyte and embed themselves within the carbon atomic structure: a process known as intercalation.
The Chalmers team’s research has focused around determining what is the optimum structure for carbon fibres based on the polymer polyacrylonitride (PAN) to both store energy by intercalating lithium and act as reinforcement for a polymer composite. PAN-based fibres have much higher electrochemical capacity than fibre is based on pitch, they found.
In the journal Multifunctional Materials, they describe how fibres with small and poorly oriented crystals have good electrochemical properties but low stiffness, while fibres with large and well oriented crystals are very stiff but have electrochemical properties too poor to act as structural battery components.
In general, “good” battery fibres are slightly stiffer than steel, while “poor” battery fibres are 10 times stiffer. ” A slight reduction in stiffness is not a problem for many applications such as cars. The market is currently dominated by expensive carbon fibre composites whose stiffness is tailored to aircraft use. There is therefore some potential here for carbon fibre manufacturers to extend their utilisation,” Asp said.
To read the full story, click here: www.theengineer.co.uk